Carbon nanodots as light-activated peroxidase nanozyme for eco-friendly leaching of copper from scrap

Abstract

The copper is the second largest strategic raw material. Since there is a huge gap between copper production and consumption, a green and eco-sustainable recycling technology is necessary that is able to process the copper from secondary sources of waste and scraps. Here we demonstrate the photo-oxidising properties of pyrrolic nitrogen-dominated carbon nanodots as eco-friendly and powerful oxidase-mimicking nanozyme for leaching of copper from metal scrap under irradiation with either ultraviolet or natural sun light (average intensity of 59 000 lux). The ultra-small nanoparticles with diameter < 5 nm were prepared by 600 W microwave-assisted pyrolysis, which might be considered as energy efficient synthetic method. The developed strategy enables to dissolve Cu metal at neutral pH range (between 5.1 – 8.3) and it might break the pH limitation for recycling of copper in the conventional chemical methods, where toxic and corrosive substances are used. The obtained yield was about 5 %, which is still not satisfactory for practical application in recycle technology. Nevertheless, according to our knowledge there is not any other reported photosensitizer nanozyme, which is capable to induce oxidation and dissolving of copper under natural light irradiation of neutral leaching solution.